Add the cumin seeds to a dry skillet. Heat gently for a minute or two until toasted and fragrant. Remove from the heat and lightly crush with a pestle and mortar or alternatively you can use the base of a rolling pin.
Thinly slice the pepper and avocado, finely slice the cabbage and chillies and roughly chop the cilantro. Add to a mixing bowl. Toss together to combine.
Add the yogurt to a small mixing bowl. Add the salt and pepper, lemon juice and ground cumin seeds. Mix together well to combine.
Spoon the cumin yogurt over the prepared vegetables. Stir well, coating the vegetables and herbs evenly in the dressing. Refrigerate until ready to serve.